The present invention relates to a method of manufacturing a photomask and a photomask technology, and particularly to a technology effective for application to a lithography technology.
A lithography technology is used as a method of transferring minute or micro patterns onto a semiconductor wafer upon manufacture of a semiconductor integrated circuit device, for example. In the lithography technology, a projection exposure apparatus or system is principally used and patterns for a photomask (hereinafter called simply a xe2x80x9cmaskxe2x80x9d) mounted to the projection exposure system are transferred onto a semiconductor wafer (hereinafter called simply a xe2x80x9cwaferxe2x80x9d) to form device patterns.
A mask pattern placed over a normal mask discussed by the present inventors is formed by pattern-processing a light-shielding film such as chromium (Cr) or the like, which is formed over a transparent quartz substrate. The pattern-processing of the light-shielding film is as follows, for example. An electron-beam sensitive resist is applied onto the light-shielding film, and desired patterns are drawn over the electron-beam sensitive resist by an electron beam drawing apparatus, followed by formation of resist patterns each having a desired shape by development. Subsequently, the light-shielding film is pattern-processed by dry etching or wet etching with each of the resist patterns as an etching mask. Thereafter, the removal and cleaning or the like of the resist patterns are carried out in order and light-shielding patterns each having a desired shape are formed over their corresponding transparent quartz substrate.
With the objective of improving resolution of recent lithography, various mask structures have been proposed. For instance, Unexamined Patent Publication No. Hei 4(1992)-136854 discloses a technology using a halftone type phase shift mask as means for improving the resolution of a single transparent pattern. According to the technology, the periphery of the single transparent pattern is rendered semitransparent. In other words, in a state in which a light-shielding portion of a mask is rendered semitransparent, slight light having sensitivity less than or equal to that of a photoresist, which passes through its semitransparent portion, and light transmitted through the transparent pattern are inverted in phase. Since the light transmitted through the semitransparent film is inverted in phase with respect to the light having passed through the transparent pattern used a main pattern, the phase is inverted at a boundary portion therebetween and a light intensity at the boundary portion approaches zero (0). Thus, the ratio between the intensity of the light transmitted through the transparent pattern and the intensity of the light at the pattern boundary portion relatively increases, and hence a light intensity distribution high in contrast as compared with a technology free of the use of the semitransparent film is obtained. The halftone type phase shift mask is one obtained by changing the light-shielding film of the normal mask to a halftone phase shift film, which in turn is manufactured substantially in the same process as the manufacturing process of the normal mask.
For example, Unexamined Patent Publication No. Hei 5(1993)-289307 discloses a technology wherein a light-shielding film is formed of a resist film with the objective of simplifying a mask manufacturing process and providing high accuracy. The present method is one using the property that a normal electron-beam sensitive resist or light-sensitive resist shields a vacuum ultraviolet light having a wavelength of about 200 nm or less. According to the method, it is not necessary to use a light-shielding film etching process step and a resist removing process step. It is therefore possible to reduce the cost of the mask, improve the accuracy of its size, and decrease defects.
For example, Unexamined Patent Publication No. Sho 55(1980)-22864 describes a mask technology for lithography, which provides patterns formed by stacking a metal film and an organic substance layer on each other. A technology has been disclosed which applies an argon ion to a photoresist pattern for pattern-processing a chrome layer lying over a main surface of a glass substrate and fixedly securing the photoresist pattern to a chrome layer pattern to thereby improve the effect of shielding each exposure light.
For example, Unexamined Patent Publication No. Sho 60(1985)-85525 discloses a technology wherein a photoresist is applied onto a mask having a defect to be recovered, and thereafter a focusing charged particle beam is applied to a small region in which the mask is to be recovered on the photoresist, thereby bringing it to carbon coating to provide its opaque state.
For example, Unexamined Patent Publication Sho 54(1979)-83377 discloses a technology wherein opaque emulsion is embedded in a local defective portion of a photomask to thereby correct each pattern.
However, it has been found out by the present inventors that the mask technologies have the following problems.
Namely, the mask technologies are respectively accompanied by a problem that they cannot cope with a change or correction of a mask pattern placed over a mask quickly. There may be cases in which in a manufacturing process of a semiconductor integrated circuit device, circuit patterns are changed or corrected to implement a semiconductor chip configuration appropriate to specifications required from customers, meet customer""s requests upon product development and manufacture, rewrite information stored in each memory, make characteristic adjustments or relieve a defective circuit. For example, Unexamined Patent Publication No. Sho 63(1988)-274156 describes that it is necessary to frequently change wirings for the purpose of writing information into a ROM upon manufacture of a semiconductor integrated circuit device with the ROM (Read Only Memory) built therein. However, since a mask substrate must be prepared for each change in design of a normal mask or for each its correction in the case of the normal mask, and a chrome film must be deposited and subjected to pattern processing, it takes time to manufacture the mask. Therefore, much time and labor are required to develop or manufacture a semiconductor integrated circuit device appropriate to specifications required from customers.
The above-described technologies, each of which forms the light-shielding patterns placed over the mask with the resist film, do not disclose a problem developed when the mask is actually used in the manufacturing process of the semiconductor integrated circuit device, a problem about the manufacture of the mask, and countermeasures thereagainst. They involve the following problems, for example.
The first is a problem that it is difficult to detect predetermined patterns used in various information detection or the like, like alignment marks, pattern measurement marks or product determination marks, etc. over a mask A mask defect inspection apparatus or exposure apparatus or system or the like being in use at present, for example, makes principal use of a halogen lamp or the like for mask alignment. Thus, when each detection mark over the mask is formed of a resist film pattern where the mask is mounted to the defect inspection apparatus or exposure system or the like, the resist film is high in optical transmittance and high contrast cannot be obtained. It is therefore difficult to detect each pattern. Therefore, a problem arises in that it is difficult to bring the mask and the defect inspection apparatus or exposure system or the like into alignment and hence satisfactory detection and exposure cannot be carried out.
The second is a problem that foreign materials are produced when the mask is mounted to the defect inspection apparatus or exposure system or the like. In the above-described technologies, the resist film over the mask is brought into direct contact with mask fixing members such as the defect inspection apparatus or exposure system or the like (fixed under vacuum, for example) where the mask is mounted to the defect inspection apparatus or exposure system or the like. Therefore, the resist film is chipped off and scraped off to thereby produce foreign materials. A problem arises in that due to the fact that the foreign materials adhere to the surface of a lens of an inspection apparatus or exposure apparatus, for example, contaminates the inside of a chamber and adhere to the surface of a semiconductor wafer, the accuracy of detection of each pattern and the accuracy of transfer thereof are brought into degradation, and failures such as a short-circuit failure in pattern and an open failure in pattern, etc. take place, thereby reducing the reliability and yields of a semiconductor integrated circuit device.
The third is a problem that when a resist film exists in a pellicle attachment portion where the pellicle is attached over a mask, the pellicle is not well attached thereto, the pellicle is apt to peel off, and foreign materials are produced upon peeling off of the pellicle.
An object of the present invention is to provide a technology capable of shortening the time required to change or correct a mask pattern placed over a mask.
Another object of the present invention is to provide a technology capable of enhancing information detection capability in a mask for causing a resist film to function as a light-shielding film.
A further object of the present invention is to provide a technology capable of restraining or preventing the occurrence of foreign materials upon an exposure process using a mask for causing a resist film to function as a light-shielding film.
The above, other objects, and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
Summaries of typical ones of the inventions disclosed in the present application will be described in brief as follows:
The present invention has a step of forming light-shielding patterns formed of a resist film for integrated circuit pattern transfer over part of a mask substrate.
The present invention also has steps of forming light-shielding patterns formed of a metal for integrated circuit pattern transfer over a mask substrate, and forming light-shielding patterns formed of a resist film for the integrated circuit pattern transfer over the mask substrate.
Further, the present invention is one wherein light-shielding patterns formed of a metal are formed over a peripheral portion of a main surface of the mask substrate upon forming the light-shielding patterns formed of the metal for the integrated circuit pattern transfer.
Furthermore, the present invention is one wherein a pellicle is fixed to the light-shielding patterns formed of the metal at the peripheral portion of the main surface of the mask substrate in contact therewith.
Still further, the present invention is one wherein openings are defined in the light-shielding patterns formed of the metal at the peripheral portion of the main surface of the mask substrate.
Still further, the present invention has the steps of forming light-shielding patterns formed of a metal for integrated circuit pattern transfer over a mask substrate, and forming light-shielding patterns formed of a resist film for integrated circuit pattern transfer over the mask substrate.
Still further, the present invention has light-shielding patterns formed of a metal for integrated circuit pattern transfer and light-shielding patterns formed of a resist film for the integrated circuit pattern transfer, both of which are provided over a mask substrate.